I've been working on a BM3 walkthrough and have found all the "extras" triggers except for pictures 9, 10, 17 and 18. (I know the locations of 17 and 18 -- I've unlocked them in the past -- but haven't yet worked out the precise circumstances to repeat it. They seem to be circumstance-based -- that is, relating to what else you have or what else you've done at the time.)

Can anyone help with these four? I'll be happy to help with any you don't know about.